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07-bootstrap-validation.md

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Validate your cluster is bootstrapped and enrolled in GitOps

Now that the AKS cluster has been deployed, the next step to validate that your cluster has been placed under a GitOps management solution, Flux in this case.

Steps

GitOps allows a team to author Kubernetes manifest files, persist them in their git repo, and have them automatically apply to their cluster as changes occur. This reference implementation is focused on the baseline cluster, so Flux is managing cluster-level concerns. This is distinct from workload-level concerns, which would be possible as well to manage via Flux, and would typically be done by additional Flux configuration in the cluster. The namespace cluster-baseline-settings will be used to provide a logical division of the cluster bootstrap configuration from workload configuration. Examples of manifests that are applied:

  • Cluster Role Bindings for the AKS-managed Azure AD integration
  • AAD Pod Identity
  • the workload's namespace named a0008

  1. Install kubectl 1.24 or newer. (kubectl supports ±1 Kubernetes version.)

    sudo az aks install-cli
kubectl version --client

    Starting with kubectl 1.24, you must also have the kubelogin credential (exec) plugin available for Azure AD authentication. Installing kubectl via az aks install-cli does this already, but if you install kubectl in a different way, please make sure kubelogin is installed.

  2. Get the cluster name.

    AKS_CLUSTER_NAME=$(az aks list -g rg-bu0001a0008 --query '[0].name' -o tsv)
echo AKS_CLUSTER_NAME: $AKS_CLUSTER_NAME

  3. Get AKS kubectl credentials.

    In the Azure Active Directory Integration step, we placed our cluster under AAD group-backed RBAC. This is the first time we are seeing this used. az aks get-credentials sets your kubectl context so that you can issue commands against your cluster. Even when you have enabled Azure AD integration with your AKS cluster, an Azure user has sufficient permissions on the cluster resource can still access your AKS cluster by using the --admin switch to this command. Using this switch bypasses Azure AD and uses client certificate authentication instead; that isn't what we want to happen. So in order to prevent that practice, local account access (e.g. clusterAdmin or clusterMonitoringUser) is expressly disabled.

    In a following step, you'll log in with a user that has been added to the Azure AD security group used to back the Kubernetes RBAC admin role. Executing the first kubectl command below will invoke the AAD login process to authorize the user of your choice, which will then be authenticated against Kubernetes RBAC to perform the action. The user you choose to log in with must be a member of the AAD group bound to the cluster-admin ClusterRole. For simplicity you could either use the "break-glass" admin user created in Azure Active Directory Integration (bu0001a0008-admin) or any user you assigned to the cluster-admin group assignment in your cluster-rbac.yaml file.

    az aks get-credentials -g rg-bu0001a0008 -n $AKS_CLUSTER_NAME

    ⚠️ At this point two important steps are happening:

    • The az aks get-credentials command will be fetch a kubeconfig containing references to the AKS cluster you have created earlier.
    • To actually use the cluster you will need to authenticate. For that, run any kubectl commands which at this stage will prompt you to authenticate against Azure Active Directory. For example, run the following command:
    kubectl get nodes

    Once the authentication happens successfully, some new items will be added to your kubeconfig file such as an access-token with an expiration period. For more information on how this process works in Kubernetes please refer to the related documentation.

  4. Validate your cluster is bootstrapped.

    The bootstrapping process that already happened due to the usage of the Flux extension for AKS has set up the following, amoung other things

    • AAD Pod Identity
    • the workload's namespace named a0008
    • Installed kured
    kubectl get namespaces
kubectl get all -n cluster-baseline-settings

    These commands will show you results that were due to the automatic bootstrapping process your cluster experienced due to the Flux GitOps extension. This content mirrors the content found in cluster-manifests, and commits made there will reflect in your cluster within minutes of making the change.

The end result of all of this is that kubectl was not required for any part of the bootstrapping process of a cluster. The usage of kubectl-based access should be reserved for emergency break-fix situations and not for day-to-day configuration operations on this cluster. Between templates for Azure Resource definitions, and the bootstrapping of manifests via the GitOps extension, all normal configuration activities can be performed without the need to use kubectl. You will however see us use it for the upcoming workload deployment. This is because the SDLC component of workloads are not in scope for this reference implementation, as this is focused the infrastructure and baseline configuration.

Alternatives

Using the AKS extension for Flux gives you a seemless bootstrapping process that applies immediately after the cluster resource is created in Azure. It also supports the inclusion of that bootstrapping as resource templates to align with your IaC strategy. Alterantively you could apply bootstrapping as a secondary step after the cluster is deployed and manage that process external to the lifecycle of the cluster. Doing so will open your cluster up to a prolonged window between the cluster being deployed and your bootstrapping being applied.

Furthermore, Flux doesn't need to be installed as an extension and instead the GitOps operator of your choice (such as ArgoCD) could be installed as part of your external bootstrapping process.

Recommendations

It is recommended to have a clearly defined bootstrapping process that occurs as close as practiable to the actual cluster deployment for immediate enrollment of your cluster into your internal processes and tooling. GitOps lends itself well to this desired outcome, and you're encouraged to explore its usage for your cluster bootstrapping process and optionally also workload-level concerns. GitOps is often positioned best for fleet (many clusters) management for uniformity and its simplicity at scale; a more manual (via deployment pipelines) bootstrapping is common on small instance-count AKS deployments. Either process can work with either cluster topologies. Use a bootstrapping process that aligns with your desired objectives and constraints found within your organization and team.

Next step

▶️ Prepare for the workload by installing its prerequisites